The present invention relates to fluid control systems for use with combustion apparatus, and in particular to such a system for controlling the safe burning of gas at the main burner.
As is well recognized, it is imperative that a fluid control system employed to control the flow of fuel to combustion apparatus operate immediately to stop the flow of fuel to the main burner if the pilot burner is inoperative.
Heretofore, most fuel control systems have included safety valves, generally operated by a thermo-couple provided to sense heat produced as a result of combustion of fuel at the pilot burner. If a pilot outage were to occur, the thermo-couple reacts to the reduction in generated heat to place the safety valve in a closed position to discontinue or prevent flow of gas to the main burner.
An example of the prior art is illustrated in U.S. Pat. No. 3,240,257. In the cited patent the illustrated control system includes a valve having two serially connected valves mounted within a common housing. One of the valves is responsive to a thermostat provided to sense demands for heat in a space served by the combustion apparatus and the other valve is responsive to the thermo-couple associated with the pilot burner. If the safety valve disclosed in the prior art patents fails to function as required, and fails in an open position, there is no backup capability in the control system to prevent continued flow of raw gas to the main burner. Thus, when the thermostat senses that heat is required in the space, the valve responsive thereto will open, even though the gas will not be ignited due to the inoperability of the pilot burner.
The present invention contemplates a single valve assembly for use in a fluid control system that includes at least two valves, each of which function independently to prevent the flow of gas to a main burner if the pilot burner is inoperative. The single valve assembly may be readily and economically installed in control systems serving combustion apparatus already in commercial use.